I have a 2018 Ford F-150 Lariat SuperCrew FX4 with the 3.0L diesel. I bought it for running around, a comfortable commuter, not necessarily for any towing.
But I ended up towing a R-Pod RP-180 and never had an issue. Driving I-75 from Atlanta to the last Goshen rally and back was a non-issue. I averaged 15MPG, overall, with the cruise control set at 65MPH while towing. When not towing I average around 22-23MPG in metro Atlanta traffic.
My trucks weak spot, for serious towing, is indeed the cargo capacity mine is rated at 1,276 pounds. Adding that nice ARE topper ate about 200+ pounds of that capacity. But an R-Pod RP-180 is light enough, the UVW is 2,950 pounds, and my loaded tongue weight was around 400 pounds, so that it wasn't an issue.
My F-150 diesel didn't cost any more than a regular F-150 Lariat to purchase. Ford was giving a rebate of $5K on diesels which is only a $4k option for the 3.0L. With the other rebates and X-Plan it was very affordable and is has all the toys I wanted.
An oil change is only $15 more than an oil change on my previous gas 5.0L F-150 XLT. The 3.0L diesel only uses 6 quarts of oil so it isn't that big of deal. Especially when you consider my 5.0L F-150 averaged around 14MPG driving locally. I've had "big" diesels before, a 7.3L Excursion and F-250's and they did cost considerably more...this one doesn't.
I see the Eco-diesel pick ups as a local commuter and light duty truck. That is what I wanted. I don't need, or want, a 3/4 ton or one ton truck. I no longer tow a TT so it is a moot point, in my case, of what can it tow. It will tow anything I want to tow.
I'm quite happy with my Eco-diesel. If you understand their limitations they can be a very good vehicle.
I've attached a picture I took in a rest stop on the way home from Goshen. After all it didn't happen without pictures...